Mode of straining saws by atmospheric pressure



UNTTED sTaTns PATENT onnion.

A. BROWN AND A. COFFIN, JR., OF SABINE CITY, TEXAS.

MODE OCE STRAINING SAWS BY ATMOSPHERIC PRESSURE.

Specification of Letters Patent No. 13,422, dated August 14, 1855.

To all wiz-0m t may concern.'

Be it known that we, A. BROWN and A. COFFIN, Jr., of Sabine City, in the county of Jefferson and State of Texas, have invented a new and useful Improvement in Atmospheric Straining Arrangements of Reciprocating Saws; and we do hereby declare that the following is a full, clear, and exact description of the same, reference being had to the annexed drawings, making a part of this specification, in which- Figure l, is a transverse vertical section of a saw frame,with our improvement attached. Fig. 2, is a front view of ditto.

Similar letters of reference indicate corresponding parts in the two figures.

Our improvement has reference to that class of atmospheric straining arrangements in which a cylinder is arranged at either end of the saw, that is one cylinder above and the other cylinder below and the two cylinders open at their inner ends and having pistons within them arranged to pull on the two ends of the reciprocating` saw by simple atmospheric pressure caused by producing a vacuum behind the pistonsthat is between the pistons and the cylinder heads. Our invention relates to the mannerY of producing this vacuum in the said arrangement, which arrangement has before been variously applied for the same purpose and has been used in numerous inventions, patented and otherwise, some of them employing steam as the agent for producing the pulling action on the pistons, others compressed air, and others as before adverted to simple atmospheric pressure by aid of a vacuum in the cylinders as described, In the latter of these arrangements, to which our improvement relates, it has been usual to connect the closed portions of the two cylinders by a pipe from which a branch was projected to a separate air pump that being set in motion served to exhaust the cylinders of the straining pistons of the air contained in them. Our invention simplies this arrangement and obtains the necessary vacuum in the cylinders of the straining pistons, by dispensing with the connecting pipes and exhaust pump re ferred to, and by providing the cylinders of the straining pistons arranged as described with a freely hung and acting snifting valve, as will be more minutely hereafter mentioned orspecied, and whereby, the reciprocating action of the saw itself is made to produce the necessary vacuum in the cylinders of the straining pistons.

In the accompanying drawing F reprsents the reciprocating saw attached at its ends by pins b to cross heads E E.

H is the revolving driving shaft of the saw to which it communicates reciprocating motion by means of a pit-man K loosely attached to the lower cross head E of the saw and operated by a wrist pin on a wheel J fast to the revolving shaft I-I.

The saw is made to reciprocate in a true vertical course by guides G along or up and down which the cross heads E E slide. These guides Cr are firmly connected to the fixed framing A of the mill; and firmly attached to the said fixed framing, above and below, are the vacuum cylinders B B provided with heads, or closed, at their outer ends, but open at their inner ends. In these cylinders, the straining pistons C C are arranged, and connected, by rods I), to the cross heads E E of the saw and made to pull on either end of the saw by ordinary atmospheric pressure acting on the faces of the pistons exposed to the inner o1' open ends of the cylinders, and thus straining the saw or keeping it straight and free from buckling, a vacuum being maintained between the pistons and closed ends or heads of the cylinder, by which means the simple atmospheric pressure is made available as a straining force, the pistons of course reciprocating with the saw as in other arrangements of the liind. In this arrangement and action there is nothing new.

Our improvement consists in the following new and useful arrangement of devices in connection with the said arrangement of pistons and cylinders in relation to the saw, to produce the necessary vacuum specified.

We provide the closed ends or heads of the cylinders with freely hung and operating snifting valves a a arranged to open outwardly. Previously to starting the cut-on feeding the log or board up to the saw, we give the saw one double reciprocating action. This suffices to expel the air out of the cylinders B B by the pistons C C forcing the air through the snifting valves a a when these valves close by the pressure of the atmosphere on the outside, and, as the said valves and pistons are constructed to fit close or air tight, no air afterward will enter 'oetween the pistons and closed ends or heads of the cylinders, and thus the pistons are eX posed to atmospheric pressure on their eX- posed faces only which causes them as they reciprocate to pull on the two ends of the saw and keep it taut, as the log or board is fed up to the cut and operated on by the saw. But should a slight leakage of the pistons and valves occur, which'will not be the case if these devices are carefully and properly constructed, then the mill should be stopped, the saw relieved of its Ycut on the log or board, and the saw reciprocated to eX- pel the air as before by the pistons forcing the air through the snifting valves a a, when the feed of the logrmay be renewed and the operation of sawing continued. The necessity for thus freeing the cylinders of air however, after the first operation of clearing them, will be seldom requisite if the pistons and valves are fitted what is termed. air tight when the leakage can be but little and at the most not su'liicient to vitiate the vacuum sufliciently to destroy the straining action of the pistons on the saw before the one cut down or along the log is taken, when giving the saw a double reciprocating action to clear the cylinders while the log is being adjusted for a fresh cut is a matter of no importance and is equivalent to no stoppage of the mill. Thus the snifting valves a a, it will be observed do not operate with every reciprocating action of the saw, but only when it is necessary to clear the cylinders of air, and as these valves operate freely and when no cut is on the saw, and only reciprocating the saw slowly to clear the cylinders, the saw will not be buckled by the operation of clearing the cylinders, While, when once cleared, the pistons in them will, by the atmospheric pressure on their exposed faces, pull on the saw to strain it. By this means, the reciprocating action of the saw itself is made to produce the necessary vacuum, and the objectionable complication of connecting pipes, branches and separate eX- haust pump or pumps is avoided.

le claim nothing new of itself in the ar- I to the saw and the pistons and valves oper.

ate together as specified, whereby the reciprocating action of the saw is made to clear the cylinders, without the aid of a separate exhaust pump as set forth.

A. BROVN. ABEL COFFIN, JR.-

Witnesses:

JoHN VoNDY, BENJ. GRANGER. 

